The proposed research is directed toward understanding the effect of the physiological environment on the degradation of polymeric biomaterials. Accelerated in vivo and in vitro methods will be used to study biodegradation of polyurethane elastomers used in cardiovascular applications. A new method of accelerated in vitro testing, stress-enhancement, will be used. A model poly (alpha-amino acid) elastomer will be used to gain a fundamental understanding of the enzymic degradation mechanism.